Support for CONNECT BY

[jmhain]

This adds support for the CONNECT BY operator, supported by Snowflake, Redshift, and MS SQL.

A bit of awkwardness is the PRIOR expressions used to refer to the upper level in the CONNECT BY relationships. These expressions are only valid in this context, and prior is a perfectly valid identifier elsewhere. Trying to thread that context through the call stack was resulting in a massive diff, so I added some state to the parser to avoid that. Happy to change this is reviewers are not fond of that approach.

[coveralls]

Pull Request Test Coverage Report for Build 8852954812

Details

• 161 of 189 (85.19%) changed or added relevant lines in 15 files are covered.
• 6 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.03%) to 89.214%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/dialect/generic.rs	1	2	50.0%
src/dialect/mod.rs	1	2	50.0%
src/dialect/mssql.rs	1	2	50.0%
src/dialect/redshift.rs	1	2	50.0%
src/dialect/snowflake.rs	1	2	50.0%
src/ast/query.rs	5	7	71.43%
src/parser/mod.rs	34	37	91.89%
src/test_utils.rs	0	4	0.0%
tests/sqlparser_common.rs	99	113	87.61%

Files with Coverage Reduction	New Missed Lines	%
tests/sqlparser_common.rs	6	89.58%

Totals
Change from base Build 8852365976:	-0.03%
Covered Lines:	23622
Relevant Lines:	26478

---

💛 - Coveralls

[alamb]

Thank you very much for this contribution @jmhain -- I am truly sorry for the delay in review.

I think the approach taken by this PR looks good to me. In my opinion, all that is needed prior to merge is:

1. Some additional comments (I left some suggestions)
2. A few negative test cases

Thanks again for such an easy to read and review PR

[alamb]

Marking as Draft to signify this PR is no longer waiting on review. Please mark it as ready for review when it is ready for another look.

[jmhain]

@alamb Many thanks for the review feedback, I greatly appreciate it! And sorry for the delay in getting back to this. So I learned that MS SQL and Redshift both also support CONNECT BY, and I did some more testing and found that my approach before was really only well suited to Snowflake, so I reworked this significantly. I also added some more tests. Thanks again!

[jmhain]

Just resolved conflicts on this again cc @alamb

[alamb]

Thanks again @jmhain

[alamb]

Looks like there is a conflict (perhaps with one of your other PRs 😆 ) -- if you can resolve that I'll merge this PR in.

Thanks again

[jmhain]

@alamb Done, thank you!

[alamb]

🚀